GNU LD: dynamic library loading a vector of strings crashes - but array of strings do not.

[Rakesh Kumar]

Hi -
  I have an issue with a vector of strings in a dynamic library.
I am posting a scaled down version of the code. Sorry - if this one is
too long .

dynstr.c :
-----------
#include "dynstr.h"
#include "dynapi.h"

#include <string>
#include <vector>
#include <iostream>

using namespace std;

dynstr::dynstr() {
}

dynstr::~dynstr() {
}

void dynstr::allocVectorOfStrings() {
    std::vector<std::string> * vt = new std::vector<std::string>();
    vt->reserve(50);
    for (size_t i = 0; i < vt->capacity(); ++i) {
        std::cout << "We are probably ok" << i << "\n";
        vt->operator[](i).reserve(40);
    }
    delete vt;
}

void dynstr::allocArrayOfStrings() {
    std::string vt[50];
    for (size_t i = 0; i < 50; ++i) {
        std::cout << "We are probably ok" << i << "\n";
        vt[i].reserve(40);
    }
}

void run() {
    dynstr * p = new dynstr;
    p->allocArrayOfStrings();
    delete p;
}

void run1() {
    dynstr * p = new dynstr;
    p->allocVectorOfStrings();
    delete p;
}



dynstr.h:
-----------
#ifndef DYNSTR_H_
#define DYNSTR_H_

class dynstr {
public:
    dynstr();
    virtual ~dynstr();

    void allocVectorOfStrings();
    void allocArrayOfStrings();
};

#endif /*DYNSTR_H_*/


dynapi.h
------------
#ifndef DYNAPI_H_
#define DYNAPI_H_

extern "C" {

        void run();


        void run1();

}
#endif /*DYNAPI_H_*/


strcrash.cpp:
----------------
#include <dlfcn.h>
#include <iostream>
#include <cstdlib>

int main(int argc, char * argv[]) {
        if (argc != 2)
        {
                std::cout << "Enter either run / run1 as the argument
\n";
                exit(EXIT_FAILURE);
        }

        void * handle = dlopen("libdynstr.so", RTLD_NOW);

        if (!handle) {
                dlerror();
                exit(EXIT_FAILURE);
        }

        typedef void (* ptrtype)();

        ptrtype pf = (ptrtype) dlsym(handle, argv[1]);

        pf();

        dlclose(handle);

        return EXIT_SUCCESS;
}

Makefile:

libdynstr.so:    dynstr.cpp    dynstr.h    dynapi.h
    g++ -Wall -g -Werror -o libdynstr.so -fpic -shared dynstr.cpp

strcrash:    libdynstr.so    strcrash.cpp
    g++ -Wall -g -Werror -o strcrash    strcrash.cpp libdynstr.so -ldl


Execution:

./strcrash run
   This creates an array of strings with no issues whatsoever.

./strcrash run1
   This creates a vector of strings and crashes at the first call when
we try to reserve memory
for the first string in the vector with a SIGSEGV .

   I am unable to understand the behavior here.  This is a scaled down
version of the problem in actual code. Can someone explain me what
could be going wrong here.